Inspect the connector on the drawbar that plugs into the tender. No bent pins, no folded over plastic on the connector that might prevent it from seating fully.
If that is ok, put both on the side on a table and press drawbar into the tender connector firmly. Visually see that it is seated. When done right it takes good pressure to remove it. Once you see it fully seated and feel the necessary pressure you will be more capable to seat it when on the track, but many just do it on the side and then move it to the track. G
